2017 Addendum
Anthropology is a rapidly developing area of knowledge, largely thanks to advances in DNA analysis and genetic research.
Back in 2011 the first Aboriginal genome was sequenced from a 90-year-old tuft of hair (Nature: 22 September 2011).
| An analysis of his genome indicates that his ancestors started their journey more than 60,000 years ago, branching off from humans who left Africa. The ancestors of contemporary Europeans and most other Asians probably went their separate ways less than 40,000 years ago, according to Willerslev's team. Ancient relations Like other populations outside Africa, the Australian Aboriginal man owes small chunks of his genome to Neanderthals. More surprisingly, though, his ancestors also interbred with another archaic human population known as the Denisovans. This group was identified from 30,000–50,000-year-old DNA recovered from a finger bone found in a Siberian cave. Until now, Papua New Guineans were the only modern human population whose ancestors were known to have interbred with Denisovans. A second study incorporating genomic surveys from different Aboriginal Australians paints an even clearer picture of their ancestors' exploits with the Denisovans. Researchers led by Mark Stoneking at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, calculated the portion of Denisovan ancestry found in the genomes of 243 people representing 33 Asian and Oceanian populations. Patterns of Denisovan interbreeding in human populations could reveal human migration routes through Asia, reasoned the team. The paper is published today in the American Journal of Human Genetics |
Last year a team headed by: Malaspinas, AS.; Westaway, M.; Muller, C.; et al. published A genomic history of Aboriginal Australia. (Nature 538, 207–214, 2016).
They generated high-coverage genomes for 83 Aboriginal Australians (speakers of Pama–Nyungan languages) and 25 Papuans from the New Guinea Highlands.
They found that Papuan and Aboriginal Australian ancestors diversified 25–40 thousand years ago, suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania).
Yet all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10–32 thousand years ago. with limited gene flow from this region to the rest of Australia, during the Holocene epoch (past 10,000 years) they inferred a population expansion in northeast Australia consistent with the spread of the Pama–Nyungan languages.
They estimated that Aboriginal Australians and Papuans diverged from Eurasians 51–72 thousand years ago, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations.
Finally, they found evidence of selection in Aboriginal Australians potentially associated with living in the desert.
Queensland's Griffith University’s Research Centre of Human Evolution (RCHE) was a major contributor to this multinational study. RCHE Professor David Lambert, one of the many contributing authors, added in Griffith News (20 September 2016) that: the differentiation of the ancestral Australian population ~31,000 years ago into subgroups was likely due to the formation of the central desert acting as a barrier to subsequent migrations.
He added that the unique morphological and physiological adaptations, identified in Aboriginal Australians living in the desert areas today, may have developed as specific biological means of coping with those highly challenging environments.
“In particular, the evidence suggests that desert groups are able to withstand sub-zero night temperatures without showing the increase in metabolic rates observed in Europeans under the same conditions,” Professor Lambert said.
This week the older practice of digging up artefacts, together with improved dating techniques, also made a seminal contribution. A team headed by Dr Chris Clarkson, from the University of Queensland, published their findings from a dig at Madjedbebe, a rock shelter in the Northern Territory in a peer reviewed article in Nature (547, 306–310, 20 July 2017).
The Abstract points out that: "The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia’s megafauna."
The paper reports a large number of human manufactured artefacts including: grinding stones, ground ochres, ground-edge hatchet heads and the world's oldest-known use of reflective minerals, were found deeply buried, surrounded by contemporary sediments that have been independently (both at the University of Wollongong and the University of Adelaide) radiocarbon and optically dated (luminescence dating -revealing when grains of sand were last exposed to sunlight) at 65,000 (+/- 5,000) years old. This pushes back previous evidence for human habitation by around 15,000 years.
Figure 1: Site location and stratigraphy, showing the location of Madjedbebe, makes reference to the lower sea levels at the time (65 ka). Compare this to the similar map of Sahul above.
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| a, Regional map showing the location of Madjedbebe in relation to the coastline at 65 ka and the current coastline (white line), and other ancient archaeological sites in Australia and southeast Asia (bathymetric data GEBCO 2014 Grid, version 20150318, http://www.gebco.net). b, Location of Madjedbebe in relation to other key archaeological sites in Kakadu National Park, and the location of the high sea-level stand during the last marine transgression about 6-7 ka (topographic data Geoscience Australia 1 arc-second DEM). c, Site plan showing the 1973, 1989, 2012 and 2015 excavation squares. Squares E1-B2 were located beneath the sloping back wall. |
The Abstract concludes: "This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans."
Commentary by local academics on this paper has drawn attention to the controversy.
Professor Peter Hiscock of the University of Sydney, one of the archaeologists previously sceptical about the dates, reportedly told the ABC: "the new study had convinced him it was the oldest site in Australia"; although he thought the date of 65,000 years was "optimistic".
Professor Hiscock is reported as saying that the significance of this "great discovery" is: "what it tells us about Australia's first people and their journey out of Africa."
"The artefacts in this site are unambiguously the evidence for the time at which Homo sapiens reach Australia," Professor Hiscock is reported as saying. "The artefacts indicated the first Australians were able to quickly adapt to their new environment."
"What we are seeing is that from the moment people are arriving in Australia they are exploiting the landscape, they are creating artwork in their shelters, and they are inventing new kinds of technologies, such as ground-edge axes, which are older than anywhere else in the world."
"Probably that level of sophistication is the reason why they were able to move from Africa to Australia."
"What we don't know is when they left Africa," Professor Hiscock is reported as saying
The ABC also interviewed palaeoanthropologist Michael Westaway of Griffith University. He is reported as agreeing that the "foundational" study would make scientists take a fresh look at that (out of Africa) question.
"The latest genetic evidence indicates that humans moved out of Africa about 72,000 years ago - although there is archaeological evidence they may have been in the Near East 110,000 years ago," Dr Westaway is reported as saying.
"It means that within several thousand years, Homo sapiens were in Australia... That's a very rapid expansion across the globe," Dr Westaway is reported as pointing out.
"Once they moved out of Africa, Homo sapiens bred with Neanderthals and Denisovans before moving into South-East Asia then into the supercontinent of Sahul - what is now New Guinea and Australia."
"The new dates also indicate modern humans lived in the same region as the ancient, now extinct, Homo floresiensis aka 'the hobbit', for at least 15,000 years," Dr Westaway is reported as commenting.
Alan Cooper at the University of Adelaide reportedly told New Scientist that he is perplexed by the discovery, given that nothing so ancient is found anywhere else in Australia. “We know these people were fast movers – they moved very quickly from Africa to Asia to Australia,” he told them. “So if they did arrive in northern Australia 65,000 years ago, why did they then just sit down and wait 15,000 years before spreading to the rest of the country?”
Adding to the mystery is the fact that it is unclear where the first Australians came from. The easiest route into Australia is via the chain of islands directly to the north, but there is little evidence that Homo sapiens was present on these islands much before 44,000 years ago, Sue O’Connor from the Australian National University is reported as telling New Scientist.
"This is an evolving picture, though. For instance, there is some evidence that H. sapiens reached a more northerly island of South-East Asia – Luzon in the Philippines - 67,000 years ago."
O’Connor is reported as being puzzled by the early humans’ wanderlust. "Sea levels were substantially lower 65,000 years ago, making it easier to move between Asia, Australia and the islands en route. But humans still had to cross open water stretching for 80 kilometres to make it to mainland Australia," she says. “There’s no obvious reason like climate shifts to explain the rapid movement.”
New Scientist comments that "the earlier arrival date for humans is in line with arguments that our species is responsible for the demise of some Australian megafauna. Creatures including giant versions of birds, echidnas and wombats, and tree-dwelling lions went extinct about 45,000 years ago."
Other scientists put these extinctions down to the global warming that led to sea level rise to present levels and the consequent climate changes to habitat, perhaps concurrent with human predation.
Meanwhile the geneticists have 'dug up' a whole new species of hominin, the 'Denisovans', without leaving the laboratory. The species gets its name from the remote Denisova Cave in the Altai Mountains in Siberia. Remains there resembled Neanderthal but were quickly discovered to be genetically quite different. No more bodies have been found but the dirt-diggers are busy to be the first to unearth another skeleton. In the meantime, as Denisovan remains and artefacts resembled Neanderthal we can assume that they had skills and culture similar to the Neanderthals, about whom we now know quite a bit.
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Their (Neanderthal) bodies were shorter and stockier than ours, another adaptation to living in cold environments. But their brains were just as large as ours and often larger - proportional to their brawnier bodies. Height: Males: average 5 ft 5 in (164 cm); Females: average 5 ft 1 in (155 cm) Neanderthals made and used a diverse set of sophisticated tools, controlled fire, lived in shelters, made and wore clothing, were skilled hunters of large animals and also ate plant foods, and occasionally made symbolic or ornamental objects. |
Denisovan genes have been found in dozens of locations due to cross species interbreeding with modern humans; particularly in New Guinea and elsewhere in SE Asia, just as Neanderthal genes are found in Europeans. The genes are so geographically widespread that the Denisovan species is thought to have been skilled seafarers. As genetic evidence in New Guinea and Australia suggests, they successfully crossed the 'Wallace Line' to Sahul (Australasia) sometime before New Guinea was separated.
New Scientist has published this speculation:
Thus if the latest find in the Northern Territory turned out to be Denisovan, and not modern H. sapiens at all, it would resolve a lot of mysteries around the age of the find and help to explain how Aboriginal Australians come to have 3 - 5% Denisovan ancestry. In addition it would point to a high level of Denisovian technological sophistication, similar to Neanderthal and Modern Humans, and more evidence of their seafaring skills. To resolve these possibilities the diggers now need to find some 65,000 year-old bones.
As I commented in the original article, above, if the hominin manufactured artefacts found at Lake Mungo were indeed still in their original silt layer and were thus correctly dated to 78,000 years ago, then they too probably predated the arrival of our species.
"Curiouser and curiouser!" said Alice.
Meanwhile, during the past four years since I last wrote, the geneticists have been busy elsewhere in the World too.
New Scientist has reported:
Fossils from Spain’s 'pit of bones' have yielded 430,000-year-old nuclear DNA that reveals Neanderthals in the making. As least 28 hominin skeletons have been recovered from a pit at the Sima de los Huesos site in the Atapuerca mountains of northern Spain. An analysis of DNA pulled from one skeleton suggests the tribe may be ancestral to both the Neanderthals and their east Eurasian contemporaries, the Denisovans.
The fossils resemble Neanderthals, which evolved some 100,000 years later. But their mitochondrial DNA is more similar to that of Denisovans, who also lived later and thousands of kilometres away, in southern Siberia. Other evidence is growing to suggest that the the split between modern humans and the Neanderthals and Denisovans occurred about 765,000 years ago.
There is increasing evidence that these early hominins had ritual and perhaps language. One body found in the 'pit of bones' is that of an individual who was killed by two blows to the head with either a spear or a stone axe, before being thrown into the pit, perhaps as part of an early funeral ritual.
“The only possible manner by which a deceased individual could have arrived at the site is if its cadaver were dropped down the shaft by other hominins,” says Nohemi Sala from Complutense University of Madrid: “Middle Pleistocene hominins were already engaging in funerary behaviour.”
It is now thought that a hominin, earlier than Neanderthals and Denisovans or modern humans, left Africa a million years earlier than modern humans and spread across the Eurasian continent. In Europe these proto-humans became known as Homo Heidelbergensis, as the first specimen was found in a sandpit near Heidelberg, but there seem to have been several subspecies, spread over a period of at least half a million years. Early examples are distinguished by a very prominent brow-ridge large face and large jaw. Their brains were considerably smaller than H. Neanderthalensis (or ours) but they were capable, co-operative hunters, used fire and manufactured sophisticated weapons, including wooden spears and intricately fashioned stone axes.
According to the Smithsonian:
| This species may reach back to 1.3 million years ago, and include early humans from Spain (‘Homo antecessor’ fossils and archaeological evidence from 800,000 to 1.3 million years old), England (archaeological remains back to about 1 million years old), and Italy (from the site of Ceprano, possibly as old as 1 million years). Comparison of Neanderthal and modern human DNA suggests that the two lineages diverged from a common ancestor, most likely Homo heidelbergensis, sometime between 350,000 and 400,000 years ago – with the European branch leading to H. neanderthalensis and the African branch (sometimes called Homo rhodesiensis) to H. sapiens |